Reversible agglomeration of powders for aerial dissemination

ABSTRACT

Powders are agglomerated by solid binders that vaporize when the agglomerates are aerially dispersed from an airplane, a specially-equipped dissemination vehicle (truck), etc. The biologically active powders are then available in their original particle size. The powders can be, for example, a pesticide, etc.

United States Patent Braude et al.

[ 1 Sept. 5, 1972 [73] Assignee: WTL. (Trace Etta, New York,

-Y- [22] Filed: Aug. 14, 1969 21 Appl. No.: 850,238

[52] US. Cl. ..424/304, 71/105, 71/120.65, 424/ 16, 424/274, 424/300[51] Int. Cl. ..A61j 3/02 [58] Field of Search .....7l/105, 120.65;424/304,- 16,

[56] References Cited UNITED STATES PATENTS 2,306,434 12/ 1942 Goodhueet al. ..21/58 2,657,164 10/1953 Buntin ..424/192 3,250,798 5/ 1 966Shulgin ..71/105 3,403,993 10/ 1968 Hoff ..71/65 3,151,969 10/ 1964Stevens ..424/78 X FOREIGN PATENTS OR APPLICATIONS 601,666 5/1948 GreatBritain 609,073 9/ 1948 Great Britain 1,010,191 11/1965 GreatBritain839,352 5/1952 Germany 1,155,631 5/1964 Germany OTHER PUBLICATIONSSullivan et al., J. Econ. Entomol. 34: 79- 80,,650- 653 (1941) Goodhueet al., J. Econ. Entomol. 35: 533- 536 (1942) Hildreth, Chem. Abst. 42:2050b (1948) Mayer, Chem. Abst. 47: 12745b (1953) Primary Examiner-ShepK. Rose Attorney-Kenneth E. Prince [57] ABSTRACT Powders areagglomerated by solid binders that vapon'ze when the agglomerates areaerially dispersed from an airplane, a specially-equipped disseminationvehicle (truck), etc. The biologically active powders are then availablein their original particle size. The powders can be, for example, apesticide, etc.

4 Claims, No Drawings REVERSIBLE AGGLOMERATION OF POWDERS FOR AERIALDISSEMINATION BACKGROUND OF THE INVENTION 1. Object of the Invention Anobject of this invention is to provide an improved method for aeriallydisseminating fine powders, such as agricultural pesticides, herbicidesand other toxic materials, from airplanes, trucks, etc. Other objectswill be apparent to those skilled in the art.

2. Prior Art For some pesticides to be effective, a fine particledispersion is required. Herbicides or pesticides should also consist offine particles for even distribution onto plants. When attempting todisseminate such materials from low-flying aircraft or helicopters,considerable wind drifting of the fine particles occurs which makes itdifficult to precisely cover the target areas. This drifting is causedby the wind blowing the fine particles over a distance determined by thewind velocity and the length of time in the air. Fine particles settlevery slowly. Solid agent powder dissemination equipment has beendeveloped, but to achieve reasonable target effectiveness at high windvelocities or turbulence, the airplane or helicopter must fly at a verylow altitude.

BROAD DESCRIPTION OF THE INVENTION The process of this inventioninvolves agglomerating fine particles, which have a mean particlediameter between 0.01 micron and l millimeter and which are biologicallyactive, by means of a solid, volatile binding material into agglomerateshaving a means particle diameter between 0.5 microns and 2 centimeters.The agglomerates can be stored under conditions which keep the bindingmaterial binder) in the solid state until they are used. Theagglomerates are accurately aerially disseminated onto target areas,whereupon the binding material vaporizes and the fine particles in theagglomerates are dispersed as individual particles. An additionaladvantage of this process is the elimination of dusting problemsprevalent with fine particle products when they are disseminated,handled, etc.

An important consideration is the ready reaerosolizability anddisintegration of the pellets. To achieve ready reaerosolizability andprovide for a uniform distribution and coverage of the desired targetareas by the product requires a fine particle relatively free ofagglomerates or aggregates. It was found that the method of thisinvention does not change the reaerosolizability of the originalmaterial, and that photomicrographs prepared of the powders beforetreatment, and after agglomeration and redispersion show similar sizeparticles.

The invention also includes an article of manufacture which areagglomerates having a mean particle diameter between 0.5 microns and 2centimeters. The agglomerates are comprised of fine particles having amean particle diameter between 0.01 micron and 1 millimeter and a solid,volatile binder. The fine particles incorporated into the agglomeratesare biologically active.

DETAILED DESCRIPTION OF THE INVENTION The fine particles to be dispersedare preferably spherical in shape, but can have essentially any shape.

The mean particle size of the particles can range between 0.01 micronand 1.0 millimeter, although preferably between 1 and 10 microns. Thefine particles are biologically active in some manner, for example, mayact as fungicides, herbicides, pesticides, bactericides, etc., mayeffect vegetation e.g., be a defoliant, etc.), and so forth. The fineparticles to be dispersed can be, for example, a pesticide, a herbicide,etc.. Specific examples are 3-( 3,4-dichlorophenyl)-l ,1- dimethylurea(Darmex, a herbicide), l-napthyl N- methyl-carbamate( Seria, a systemicinsecticide), N- trichloromethylthio-4-cyclohexene- 1 ,Z-dicarboximide(Captan, a fungicide), the reaction product of NCCl-I CN andchlorobenzaldehyde, and hydrophobic form of the immediately aforegoingreaction product.

The binding materials must be solid and volatile (preferably at roomtemperature), and can be organic or inorganic. The term solid includesgelled, congealed, coagulated, etc. Examples of useful bindingmaterials, having relatively low melting or sublimation points, are:camphor; p-dichlorobenzene; naphthalene; trioxane; ammonium carbamate; 1,6- dichloronaphthalene; l,4-naphthoquinone; 5-chloro-2- nitrophenol;2,4-diiodophenol; 2,4,6-tribromophenol; polyoxyvaleric acid;o-xyloquinone; p-xyloquinone; B- sulfur trioxide; 2-phenylchromone;dicyclopentadiene; p-bromoanisole; 4-methoxy-3-ethoxybenzaldehyde;achloroacrylic acid; and solid CO Between 0.1 and percentby weight ofthe binding material based upon the weight of the fine particles used)are used, but preferably between 5 and 20 percent by weight of thebinder is utilized.

The binding material must be volatile or sublime) to a reasonable extentat the temperatures encountered in the redispersing stage, which will bea maximum temperature of about F. The binding material should not be sovolatile at normal storage conditions that a problem occurs, but thisproblem can be alleviated by storing the agglomerates in sealedcontainers, with the option of pressurizing the containers. Or, anystorage and transportation of the agglomerates can be done under anatmosphere saturated with the vapors of the binder. Another bindingmethod is solid CO which is injected into a stream of flowing particles.If low temperatures are available, a small amount of water, which isfrozen by the dry CO to ice, provides an effective agglomerating medium.A cyclone device should be used in that agglomerating scheme.

The agglomerates should have a mean size (diameter) between 0.5 micronand 2 centimeters. Agglomerates in the preferred diameter range usuallyfall to earth in less than about a minute from heights of one thousandfeet and have minimal wind drift rates. Each agglomerate can include twoor more of the individual particles. The agglomerates must be capable ofstorage and handling, but must disintegrate readily after exposure toair. The agglomerate life in open air is normally a few minutes, but canbe several days in particular embodiments. That life span depends uponthe method and pressure used to form the agglomerates, the type andamount of binder used, etc.

The particles in the agglomerates need to be maintained in a looselypacked form to be easily reversible, i.e., reaerosolization byessentially spontaneous means. Therefore, agglomerate preparation shouldnot be 3 done'by using very high compression, such as by forming pelletsor by tableting under relatively high pressure. Various agglomeration orpelletizing techniques may be used provided thatthe'force or pressureused is small so as to prevent an excessively close contactbetween theoriginal particles. Examples of useful techniques include pangranulating, extrusion, pelleting, cyclone agglomerating, prilling, useof vibrators, etc. When the agglomerates are prepared by pelletizing thefine particles, it can be accomplished at room temperatureor,preferably, by maintaining the equipment and particles above thesoftening temperature of the binder. Gas pressure may be applied toprevent vaporization of the binder. The agglomerates are then cooled toprevent a breaking up thereof. Grinding may be necessary. Iftheagglomerating is done by merely admixing the particles and binder, itmay be desirable to incorporate the binder dissolved in a small amountof volatile solvent, e.g., pentane. Large amounts of volatile solventcannot be used because an irreversible agglomeration may be produced.Or, it may be desirable to grind the blend.

The agglomerates are normally stored in protective containers, free fromexposure to air. Pressure and special gases may be used during storage.Normally, the agglomerates are stored in an atmosphere saturated withvapors of the substance used as a binder. The agglomerates, so stored,should not cake into large solids, even when subjected to temperaturecycling. The term store or storing, as used herein, can encompass a veryshort time and can encompass periods of time which are essentiallytransportation periods.

To achieve an easier reaerosolization,-the original particles shouldpreferably be protected against permanent agglomeration by a suitabletreatment. Such treatments, which are well known in the art, may includeimpregnation with a silicone or silazane with or without addition offine size hydrophobic silica, to make the particles more hydrophobic asshown in US. Pat. No. 3,333,776 the pertinent portions of which arespecifically incorporated herein by reference.

The agglomerated particles are normally taken aloft to the desiredlocation in suitable dissemination equipment or containers by airplanesor helicopters. The agglomerates are then dropped, either all at once orat the desired stream rate, and fall rapidly to the ground. The droppedagglomerates disintegrate by evaporation of the binder during the fallor after impact on the ground, trees, foliage, etc. After evaporation ofthe binder, the particles should not still be agglomerated to anysignificant degree.

The term aerial dissemination, as used herein, means dispersion from anairplane, a projectile, a ground vehicle, etc. The term airplane," asused herein, includes helicopters, airplanes, dirigibles, balloons, andany other craft capable of air flight. The agglomerated particles may betaken aloft to the desired height in suitable dissemination equipment orcontainers by airplanes or helicopters. They may also be disseminated bybeing blown or projected from ground vehicles in continuous streams orbatchwise onto the area to be covered. When taken aloft by airplanes,they may then be dropped, either all at once or at the desired streamlaid, and will fall rapidly to the ground.

I The term ground vehicle used herein. may implya tractor, truck, orother vehicle capable of moving through or to the desired locatiomTheagglomerated particles may be disseminated fromthese vehicles by meansof blower devices or throwing devices, and-by use of, for instance,centrifugal force oi-similar means.

1 EXAMPLE 1" One thousand grams (powdered) of the reaction product-ofNCCH CN and chlorobenzaldehyde, 700

milliliters of Skelly F solvent, 30 grams of Cabosil SH5( a fin e sizesilica made by the Cabot Company) and Y10 grams of hexamethyldisilazanewere ball milled together for over 48 hours. The'b alls were removed ona screen and the paste dried overnight, yielding a free flowing powderof treated reaction product i of NCCH CN and'chlor'obenzaldehyde with amean particle diameter of 6 microns.

EXAMPLE 2 Ten grams of the treated reaction product of NCCl-l CN andchlorobenzaldehyde described in Example were admixed with 0.50 gram ofcamphor. The

completely evaporated. The particles obtained from the disintegratedpellets were free flowing, easily reaerosolized, and had a mean particlediameter of 6 microns, like the pretested reaction product of NCCH CNand chlorobenzaldehyde used for agglomerating.

EXAMPLE 3 Ten grams of the pretreated reaction product of NCCl-l CN andchlorobenzaldehyde from Example 1 were admixed with 0.3 gram ofparadichlorobenzene in 2.0 milliliter of pentane. After thorough mixingin a mortar, pellets were formed in a small tableting machine under lowpressure. The agglomerates were about 6 millimeters in diameter and 3millimeters thick, and were resistant to breakage and disintegration.The tablets were exposed to ambient air for 18 hours. Both the solventand the solid binding agent evaporated, yielding a free flowing readilyaerosolizable product.

Photomicrographs taken of the particles of reaction product of NCCH CNand chlorobenzaldehyde before and after addition of theparadichlorobenzene and solvent and agglomeration showed no differencein particle size (which averaged about 6 microns) or of degrees ofagglomeration.

EXAMPLE 4 A small laboratory cyclone device was connected to a carbondioxide cylinder. An inlet tube was provided into the cyclone throughwhich pretreated reaction product of NCCl-l CN and chlorobenzaldehyde inair was fed continuously from a funnel. Introducing the carbon dioxiderapidly and a small stream of reaction product of NCCH CN andchlorobenzaldehyde simultaneously into the cyclone resulted in a rapidcooling of the cyclone device due to the expansion of the carbondioxide. The exit stream from the cyclone yielded the reaction productof NCCH CN and chlorobenzaldehyde particles which were agglomerated tospherical balls of about 3 millimeters in diameter. These balls, it isbelieved, were held together by frozen moisture introduced with the air.The particles did not change in appearance on storage in a freezer at to5 F. overnight. On exposure to air at ambient temperature, rapiddisintegration occurred, yielding a free flowing readily reaerosilizablereaction product of NCCH CN and chlorobenzaldehyde powder.

EXAMPLE 5 Sgrams of the reaction product of NCCH CN andchlorobenzaldehyde, having a mean particle diameter of 6 microns, andgrams of powdered dry ice were admixed. The resultant agglomerates wereabout 1 millimeter in diameter. Some moisture absorbed from the airformed a crust around the agglomerates. The ice melted and the dry icesublimed off in about 30 minutes. The particles of the reaction productof NCCl-l CN and chlorobenzaldehyde were free flowing. The experimentwas repeated and the agglomerates were dropped about 30 feet, yielding afinely powdered reaction product of NCCH CN and chlorobenzaldehyde onimpact.

EXAMPLE 6 10 grams of the reaction product of NCCH CN andchlorobenzaldehyde, having a mean particle size of 6 microns and 1 gramof para-dichlorobenzene were admixed and peletized. Thepara-dichlorobenzenevaporized off within 2 days and the reaction productof NCCH CN and chlorobenzaldehyde was free flowing.

EXAMPLE 7 Example 2 was repeated, except that the camphor was admixedwith a very small amount of pentane before the camphor was admixed withthe reaction product of NCCH CN and chlorobenzaldehyde. The pentaneimmediately vaporized off. Similar results were obtained.

EXAMPLE 8 Example 2 was repeated, except that 10 gram of Captan wereused in place of the reaction product of NCCH CN and chlorobenzaldehydeprepared in Example 1. Similar results were obtained.

EXAMPLES 9 thru 13 Example 6 was repeated five times, except that thepara-dichlorobenzene was replaced with ammonium carbamate, trioxane,naphthalene, polyoxyvaleric acid, and B-sulfur trioxide, respectively.Agglomerates were obtained in each case and the reaction product of NCCHCN and chlorobenzaldehyde was free flowing in each case after the binderhad vaporized (or sublimed) off.

EXAMPLE 14 vExample 2 was repeated, except that the agglomerates werestored under an atmosphere saturated .with camphor vapors. Similarresults were obtained.

EXAMPLE 15 Example 2 was repeated, except that 20 gram of Carmex wereused in place of the reaction product of NCCH CN and chlorobenzaldehydeprepared in Example 1. Similar results were obtained.

EXAMPLE 16 Example 2 was repeated, except that 7 gram of Serin" wereused in place of the reaction product of NCCH CN and chlorobenzaldehydeprepared in Example l Similar results were obtained.

EXAMPLES 16 thru 21 EXAMPLE 22 200 ml. of a mixture of saturatedhydrocarbons having an average of about 6 carbon atoms per molecule(Skelly F solvent), 3 grams of a finely divided silica having a surfacearea of 325 square meters per gram and 0.5 gram of hexamethyldisilazanewere admixed.

' the admixture was placed in a US. Stonewarde BF-OO.

0.3 gal capacity, ball-mill jar and milled for 15 minutes to insuretreatment of the silica and grinding surfaces of the mill with thesilazane. grams of the pulverized reaction product of NCCH CN andchlorobenzaldehyde was added to the mixture to form a slurry. The slurrywas milled for 24 hours. The slurry was then removed from the mill andthe hydrocarbon fluidizing agent allowed to evaporate. The product was asoft cake. It was disintegrated by dry-grinding in a ball mill similarto the one above for 15 minutes to yield a freeflowing powder with .98percent of its particles smaller than 5 microns, and essentially all ofits particles smaller than 10 microns. 10 grams of the ground productwas treated by the method of Example 2 and similar results wereobtained.

What is claimed:

1. Pellets having minimal wind drift rates for accurately disseminatingfine readily re-aerosolizable powders onto target areas, said pelletshaving a mean particle diameter between 0.5 micron and 2 centimeters andconsisting essentially of bilogically active fine aerosolizableparticles having a mean particle diameter between 0.01 micron and 1.0millimeter selected from the group consisting of3-(3,4-dichlorophenyl)-l ,1- dirnethylurea, l-naphthylN-methyl-carbamate, N- trichloromethylthio-4-cyclohexenel,Z-dicarboximide and the reaction product of NCCH CH andchlorobenzaldehyde agglomerated together with an effective amount of asolid, volatile binder to maintain a loosely packed form adapted toessentially spontaneously reaerosolize said biologically activeparticles, said binderbeing selected from the group consisting ofcamphor; p-dichlorobenzene, naphthalene, trioxane;

biologically active fine particles being readily reaerosolizable and notin agglomerated form to any significant degree after volatilization ofthe binder.

2. An article of manufacture as described in claim 1 wherein said binderis camphor.

3. An article of manufacture as described in claim 1 wherein said binderis para-dichlorobenzene.

4. An article of manufacture as described in claim 1 wherein said fineparticles are the reaction product of NCCH CN and chlorobenzaldehyde.

2. An article of manufacture as described in claim 1 wherein said binderis camphor.
 3. An article of manufacture as described in claim 1 whereinsaid binder is para-dichlorobenzene.
 4. An article of manufacture asdescribed in claim 1 wherein said fine particles are the reactionproduct of NCCH2CN and chlorobenzaldehyde.